Multilayer Band-Pass Filter With Isolated Grounds for Narrower Passbands
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Solution Overview
Problem
The challenge of miniaturizing band-pass filters for compact communication devices while maintaining desired electromagnetic characteristics is hindered by strong electromagnetic coupling between inductors, which affects the filter's performance.
Innovation Solution
A multilayer band-pass filter design that integrates first and second inductors with separate ground terminals, each connected to ground but not electrically connected to each other, and includes capacitors between the inductors and ground, reducing electromagnetic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the band-pass filter is miniaturized to reduce size and footprint, then the filter meets compact communication apparatus requirements, but electromagnetic coupling between the two inductors becomes too strong
Solution Approach 1:
The patent divides the ground connection system into two separate ground terminals (first ground terminal and second ground terminal) that are electrically isolated from each other within the stack. This segmentation prevents the formation of a common ground path that would otherwise create strong electromagnetic coupling between the inductors, thereby maintaining desired filter characteristics while enabling miniaturization.
Solution Approach 2:
The patent introduces a ground electrode as an intermediary element that connects both ground terminals to the external ground, but prevents direct electrical connection between the ground terminals themselves. This intermediary structure allows each inductor to have its own independent ground reference while avoiding direct coupling paths, resolving the electromagnetic coupling issue in miniaturized filters.
2Device complexity
If a common ground terminal is used for both inductors, then the filter structure is simplified, but electromagnetic coupling between inductors increases
Solution Approach 1:
Instead of using a single common ground terminal, the patent segments the ground connection into two separate ground terminals (first ground terminal connected to first inductor, second ground terminal connected to second inductor). Each ground terminal is electrically isolated within the stack, preventing electromagnetic coupling while maintaining structural simplicity through the use of a shared ground electrode for external connection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves a narrower passband and desired electromagnetic characteristics by minimizing electromagnetic coupling between inductors, ensuring compliance with specification requirements.
Implementation Method 1
a first inductor L2 and a second inductor L3 electromagnetically coupled to each other
Implementation Method 2
a first capacitor C2 electrically connected to a second end of the first inductor L2 and integrated with the stack, and a second capacitor C3 electrically connected to a fourth end of the second inductor L3 and integrated with the stack
Data Source
AI summary
A band-pass filter includes a first inductor and a second inductor electromagnetically coupled to each other, a first ground terminal electrically connected to the first inductor, a second ground terminal electrically connected to the second inductor, and a stack for integrating the first inductor, the second inductor, the first ground terminal, and the second ground terminal. The first ground terminal and the second ground terminal are each connected to a ground and are not electrically connected to each other in the stack.